The present invention relates to the etching of dielectric materials. More particularly, the present invention is related to the selective etching of silicon carbide using a chlorine containing gas.
The manufacture of multilayer structures typically involves patterned etching of areas of the semiconductor surface that are covered by a photoresist protective material. One etching technique is reactive ion etching (RIE). This process involves positioning a semiconductor wafer in a reaction chamber and feeding etchant gases into the chamber. The etchant gases are dissociated in a radio frequency (RF) field so that ions within the etchant gases are accelerated to the wafer surface.
The accelerated ions combine chemically with unmasked material on the wafer surface and a volatile etch product is produced that is incorporated into the plasma. The concentration of the volatile etch product can be tracked in order to determine the end-point of the RIE process, i.e., when the chemical reaction has removed the desired level of material from the wafer surface. During the RIE process, a single layer or multiple layers of material or film may be removed. The materials may include, for example, silicon carbide (SiC), silicon nitride (Si3N4), PSG, silicon dioxide (SiO2), poly-silicon (PSi), or a low-k dielectric material.
A variety of patents teach the etching of SiC. U.S. Pat. No. 3,398,033 issued to Haga teaches wet etching of silicon carbide by the use of a mixture using oxygen (O2) and chlorine (Cl2) heated to between 1200° C. and 1300° C. U.S. Pat. No. 4,351,894 issued to Yonezawa teaches a plasma etch process for removing SiC using carbon tetrafluoride and optionally oxygen (O2). U.S. Pat. No. 4,595,453 issued to Yamazaki teaches using hydrogen fluoride gas (HF) in a dry etch plasma process. U.S. Pat. Nos. 4,865,685 and 4,981,551, both issued to Palmour, teach reactive ion etching of SiC using NF3 and, alternatively NF3 mixed with O2 and argon (Ar).
However, each of these patents fail to teach a method for selectively etching silicon carbide (SiC) at an etch rate that is higher than the etch rate for a low-k dielectric. Generally, SiC has been used as an etch stop layer or as a hardmask layer in dual damascene applications that employ low-k dielectric materials. As a result of having a SiC layer near a low-k dielectric materials, there has been a need for selectively etching the SiC at a faster rate than the low-k dielectric material.